Interferometric modulator for optical signal processing

• US 5,315,370 A
• Filed: 10/23/1991
• Issued: 05/24/1994
• Est. Priority Date: 10/23/1991
• Status: Expired due to Term

• Current Assignee: Jeffrey A. Bulow
• Original Assignee: Jeffrey A. Bulow
• Inventors: Bulow, Jeffrey A.
• Primary Examiner(s): Turner, Samuel A.
• Application Number:
  US07/780,786
• Time in Patent Office: 944 Days
• Field of Search: 356/345, 356/346, 356/350, 356/358, 356/356, 356/349
• US Class Current: 359/245
• CPC Class Codes: G02B 27/144 using partially transparent surfaces without spectral selectivity G02B27/147 takes precedence
• CPC Class Codes: G02B 27/145 having sequential partially reflecting surfaces

Abstract

An interferometric modulator uses a beamsplitter to produce deflected and transmitted light beams onto mirrored surfaces of a piezoelectric crystal pair, one piezoelectric crystal being driven by a modulating voltage signal, whereupon the light beams are reflected back to the beamsplitter to produce a modulated optical output signal, with the modulator being especially adaptable for use as an digital photonic clock, as a pulse width/amplitude modulator, and as a bistable optical memory cell.

Claims

1. An interferometric modulator for electromagnetic signals comprising:

means for providing an electromagnetic input signal having a first fundamental frequency;

beamsplitter means for receiving said electromagnetic input signal and separating said input signal into a reflected signal and a transmitted signal having a respective phase relationship;

first means for providing a first modulating signal;

a first reflecting means positioned a first distance from said beamsplitter means for receiving said reflected signal and returning said reflected signal to said beamsplitter means, said reflected signal having an optical path length determined by said first distance;

a second reflecting means positioned a second distance from said beamsplitter means for receiving said transmitted signal and returning said transmitted signal to said beamsplitter means, said transmitted signal having an optical path length determined by said second distance;

said first reflecting means including a modulating means responsive to said first modulating signal for varying said first distance and said reflected signal optical path length, wherein said respective phase relationship between said reflected and transmitted signals varies as said first distance is varied; and

wherein

said beamsplitter means combines said returned reflected and transmitted signals into a modulated output signal having a second fundamental frequency determined by said varying phase relationship; and

wherein

said first reflecting means includes a first piezoelectric crystal that has a distance of movement of 50 to 500 times lambda, where lambda is the wavelength of said electromagnetic input signal.

3. An interferometric modulator according to claim 1 or claim 2 wherein said first piezoelectric crystal includes a mirrored surface.

4. An interferometric modulator according to claim 3 wherein said first piezoelectric crystal is responsive to said first modulating signal for varying said reflected or transmitted signal optical path length.

5. An interferometric modulator according to claim 4 wherein said first means for providing a first modulating signal includes a voltage generator.

6. An interferometric modulator according to claim 5 wherein said voltage generator produces a first modulating signal of predetermined amplitude and frequency.

7. An interferometric modulator according to claim 6 further including second means for providing a second modulating signal and wherein said second reflecting means includes a second modulating means responsive to said second modulating signal.

8. An interferometric modulator according to claim 7 wherein said second means for providing a second modulating signal includes a voltage generator for producing a second modulating signal of predetermined amplitude and frequency, and phase relative to said first modulating signal.

9. An interferometric modulator according to claim 8 wherein said second reflecting means includes a second piezoelectric crystal having a mirrored surface.

10. An interferometric modulator according to claim 9 wherein said second piezoelectric crystal is responsive to said second modulating signal for varying said transmitted or reflected signal optical path length.

11. An interferometric modulator according to claim 1 or claim 2 wherein said electromagnetic signal has a predetermined frequency in the optical range.

12. An interferometric modulator according to claim 1 or claim 2 wherein said electromagnetic signal has a predetermined frequency in the ultraviolet range.

13. An interferometric modulator according to claim 1 or claim 2 wherein said electromagnetic signal has a predetermined frequency in the infrared range.

2. An interferometric modulator for electromagnetic signals comprising:

means for providing an electromagnetic input signal having a first fundamental frequency;

beamsplitter means for receiving said electromagnetic input signal and separating said input signal into a reflected signal and a transmitted signal having a respective phase relationship;

first means for providing a first modulating signal;

a first reflecting means positioned a first distance from said beamsplitter means for receiving said transmitted signal and returning said transmitted signal to said beamsplitter means, said transmitted signal having an optical path length determined by said first distance;

a second reflecting means positioned a second distance from said beamsplitter means for receiving said reflected signal and returning said reflected signal to said beamsplitter means, said reflected signal having an optical path length determined by said second distance;

said first reflecting means including a modulating means responsive to said first modulating signal for varying said first distance and said transmitted signal optical path length, wherein said respective phase relationship between said transmitted and reflected signals varies as said first distance is varied; and

wherein

said beamsplitter means combines said returned transmitted and reflected signals into a modulated output signal having a second fundamental frequency determined by said varying phase relationship; and

wherein

said first reflecting means includes a first piezoelectric crystal that has a distance of movement of 50 to 500 times lambda, where lambda is the wavelength of said electromagnetic input signal.

14. An interferometric modulator for producing a square wave electromagnetic signal from a sinusoidal electromagnetic signal comprising:

means for providing a sinusoidal electromagnetic input signal;

first beamsplitter means for receiving said electromagnetic input signal and for splitting said signal into a plurality of signal portions, said first beamsplitter means including a first plurality of beamsplitters;

second beamsplitter means for receiving said plurality of signal portions, said second beamsplitter means including a second plurality of beamsplitters aligned with one another, each second beamsplitter being positioned to receive one of said plurality of signal portions and for splitting said signal portions into a reflected portion and a transmitted portion;

piezoelectric crystal means comprising a plurality of pairs of piezoelectric crystals, each pair consisting of two crystals arranged at an opposing angle to one another with respect to an associated one of said second plurality of beamsplitters, each of said two crystals being positioned adjacent to a said respective second beamsplitter for receiving said reflected and transmitted signal portions, for modulating at least one of said reflected and transmitted portions, and for returning said signal portions including said at least one modulated portion to said respective second beamsplitter;

wherein said returned signal portions including said at least one modulated portion recombine in each said respective second beamsplitter to form a plurality of first modulated signals, each associated with one of said plurality of second beamsplitters; and

third beamsplitter means for receiving said plurality of first modulated signals, said third beamsplitter means comprising a plurality of third beamsplitters, each positioned relative to a respective second beamsplitter for receiving a first modulated signal from a respective second beamsplitter, said plurality of third beamsplitters being aligned with on another to combine said plurality of first modulated signals into a square wave output signal.

15. An interferometric modulator according to claim 14 further comprising support means in the form of an inverted T on which said second and third beamsplitter means and said piezoelectric crystal means are mounted.

16. An interferometric modulator according to claim 14 wherein said second and third beamsplitter means each comprises two sets of at least two beamsplitters aligned horizontally in a row wherein the row of said third beamsplitters is directly above the row of said second beamsplitters, and said piezoelectric crystal means comprises at least eight piezoelectric crystals consisting of four pairs of crystals wherein each crystal of said pair faces adjacent sides of a respective second beamsplitter.

17. An interferometric modulator according to claim 14 wherein each said piezoelectric crystal includes a mirrored surface for returning said reflected and transmitted signal portions back to a respective said second beamsplitter.

18. An interferometric modulator according to claim 14 further comprising an electric signal source means for producing a modulating signal applied to one crystal in each of said crystal pairs for modulating said reflected and transmitted light portion associated with each said second beamsplitter.

19. An interferometric modulator for modulating a digital waveform electromagnetic signal comprising:

means for providing a digital waveform electromagnetic input signal;

an input beamsplitter means for receiving said input signal and for dividing said input signal into first and second signal portions;

a first modulation means for modulating said first signal portion and a second modulation means for modulating said second signal portion and,

an output beamsplitter means for receiving said first modulated signal and said second modulated signal and for combining said first and second modulated signals into a final modulated output signal and

wherein said first modulation means comprises at least one beamsplitter for receiving said first signal portion and for dividing said first signal portion into a first signal reflected portion and a first signal transmitted portion, and a first piezoelectric crystal for receiving said first signal reflected portion.

20. An interferometric modulator according to claim 19 further including an electric signal generator for producing a first modulating signal, said first piezoelectric crystal being responsive to said modulating signal for modulating said first signal reflected portion to produce a modulated first signal reflected portion.

21. An interferometric modulator according to claim 20 wherein said second modulation means comprises at least one beamsplitter for receiving said second signal portion and for dividing said second signal portion into a second signal reflected portion and a second signal transmitted portion, and a second piezoelectric crystal for receiving said second signal reflected portion.

22. An interferometric modulator according to claim 21 wherein said second piezoelectric crystal is responsive to said modulating signal for modulating said second signal reflected portion to produce a modulated second signal reflected portion, and wherein said modulated first and second signal portions are responsive to said output beamsplitter means to produce said modulated output signal.

23. An interferometric modulator according to claim 22 wherein said second modulation means further includes a second electric signal generating means for producing a second modulating signal and a third piezoelectric crystal responsive to said second modulating signal for modulation of said second signal portion independent of modulation of said first signal portion.

24. An interferometric modulator according to claim 23 wherein said first and second signal portions comprise a digital waveform generated from an underlying carrier signal, and wherein the first signal portion digital waveform and carrier signal are in phase with the second signal portion digital waveform and carrier signal.

25. An interferometric modulator according to claim 24 wherein said third piezoelectric crystal is responsive to said second electric signal generating means for causing a phase difference between said first signal portion digital waveform and carrier signal and said second signal portion digital waveform and carrier signal.

26. An interferometric modulator according to claim 25 wherein said phase difference between first and second signal portion digital waveforms is π

/2 and the phase difference between first and second signal portion carrier signals is approximately π

/2, whereby said modulated output signal has a pulse width duty cycle that is approximately 150% of either first or second signal portion pulse width duty cycle.

27. An interferometric modulator according to claim 26 wherein said first and second signal portions are digital waveform signals and said second electric signal generating means provides a controlled variable modulating signal such that carrier signal phase difference is maintained at π

/2 for each stable state time duration of the said second electric signal and the digital waveform phase difference varies between 0 and π

, whereby pulse width modulation of said input signal is provided.

28. An interferometric modulator according to claim 25 wherein said phase difference between first and second signal portion digital waveforms is approximately zero and fixed, and the phase difference between first and second signal portion carrier signals is variable between 0 and π

, whereby amplitude modulation of said input signal is provided.

29. An interferometric modulator according to claim 25 wherein said phase difference between first and second signal portion digital waveforms is π

/2 and said phase difference between first and second signal portion carrier signals is π

, whereby a precision frequency doubler of said input signal is provided.

30. An interferometric modulator according to claim 29 wherein each of said first and second signal portions is comprised of a primary signal and a secondary signal each comprising a digital waveform generated from an underlying carrier signal, and wherein the digital waveforms of said primary and secondary signals have a phase difference of π

/2 and the carrier signals of said primary and secondary signals have a phase difference of π

, whereby a precision frequency quadrupler of said input signal is provided.

31. An interferometric modulator for providing memory storage of an optical data signal comprising:

first beamsplitter means for receiving an optical data signal and for dividing said data signal into a reflected data signal and a transmitted data signal and first optical sensing means for sensing said reflected data signal;

second beamsplitter means for receiving an optical memory operation signal and for combining said data and operation signals to produce a resultant signal, and second optical sensing means for sensing said operation signal and third optical sensing means for sensing said resultant signal;

piezoelectric crystal means with a mirrored surface, and controller means responsive to said first, second, and third optical sensing means for producing a controlling signal;

said piezoelectric crystal means being responsive to said controlling signal for altering the position of said mirrored surface, said mirrored surface arranged to reflect a portion of said resultant signal; and

third beamsplitter means for receiving a portion of said resultant signal and a signal from said mirrored surface and for combining said received signals into an output signal which indicates the contents of the optical memory storage.

32. An interferometric modulator according to claim 31 further including third beamsplitter means for initially receiving said operation signal and a clock signal, said third beamsplitter means comprising at least one beamsplitter and one mirror arranged to combine said operation and clock signals.

33. An interferometric modulator according to claim 32 operation signal is a read signal.

34. An interferometric modulator according to claim 32 wherein said operation signal is a write signal.

35. An interferometric modulator according to claim 31 wherein said first and second beamsplitter means are oriented to provide optical isolation between said operation signal and said data signal.

36. An interferometric modulator according to claim 31 including optical sensing means for detecting data even without a write signal, thereby providing an if-data-found logical operation.

37. An interferometric modulator according to claim 36 wherein said logical operation is passive.

38. An interferometric modulator according to claim 36 wherein said logical operation is active.

39. An interferometric modulator for electromagnetic signals comprising:

means for providing an electromagnetic input signal having a first fundamental frequency;

beamsplitter means for receiving said electromagnetic input signal and separating said input signal into a reflected signal and a transmitted signal having a respective phase relationship;

first means for providing a first modulating signal;

a first reflecting means positioned a first distance from said beamsplitter means for receiving said reflected signal and returning said reflected signal to said beamsplitter means, said reflected signal having an optical path length determined by said first distance;

a second reflecting means positioned a second distance from said beamsplitter means for receiving said transmitted signal and returning said transmitted signal to said beamsplitter means, said transmitted signal having an optical path length determined by said second distance;

said first reflecting means including a modulating means responsive to said first modulating signal for varying said first distance and said reflected signal optical path length, wherein said respective phase relationship between said reflected and transmitted signals varies as said first distance is varied; and

wherein

said beamsplitter means combines said returned reflected and transmitted signals into a modulated output signal having a second fundamental frequency determined by said varying phase relationship; and

wherein said first reflecting means includes a first piezoelectric crystal, said first piezoelectric crystal includes a mirrored surface, and said first piezoelectric crystal is responsive to said first modulating signal for varying said reflected or transmitted signal optical path length; and

wherein said first means for providing a first modulating signal includes a voltage generator and said voltage generator produces a first modulating signal of predetermined amplitude and frequency; and

further including second mean for providing a second modulating signal and wherein said second reflecting means includes a second modulating means responsive to said second modulating signal and wherein said second means for providing a second modulating signal includes a voltage generator for producing a second modulating signal of predetermined amplitude and frequency, and phase relative to said first modulating signal; and

wherein said second reflecting means includes a second piezoelectric crystal having a mirrored surface, and

said second piezoelectric crystal is responsive to said second modulating signal for varying said transmitted or reflected signal optical path length.